I have basic-miktex-22.10-x on Windows 10. I saw a discussion of similar error in the Internet but did not see an answer clear for me (I am a simple user without deep understanding of the program). I have been using earlier versions of LaTeX for many years but never encountered such a problem. Help would be greatly appreciated.
\documentclass[preprint,aps,amsmath,eqsecnum,fleqn]{revtex4}
\usepackage{bm}
\usepackage[dvips]{graphicx}
\newcommand{\arccosh}{\mbox{arccosh}}
\begin{document}
In $n$ region of the material there are charged donors and electrons excited from these donors
\end{document}
and texing gives
! Extra \endgroup. \document ->\endgroup \init@documenthook \set@typesize@hook \normalsize \set... l.10 \begin{document} ? ! LaTeX Error: Missing \begin{document}